Metallic thermometer



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W. A. WALES.

VMetallic Thermometer(- f No. 240,059. Patented April 12, 188i,

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"PETERS, PNnTn-UNDBRAPHER. WSIINGTON. D. C.

UNITED STATES PATENT OiEEIcEO WILLIAM A. WALES, OF NEWTON, ASSIGNOR TO THEVABURNDALE WATCH COMPANY, OF WESTON, MASSACHUSETTS.

METALLIC THERMOMETER.

SPECIFICATION forming `part of Letters Patent No. 240,059, dated April 12, 1881. Application filed December 151880. (No model.)

To all whom it may concern:

Beitknown that I, WILLIAM A. WALES, a citizen of the United States, residing at Newton, in the county of Middlesex and State of 5 Massachusetts, have invented a new and usef ful Improvement in Mechanical Thermometers,

produced with equal accuracy of any size from the small watch-charm to the turret clock-dial. I5 The general description and operation ofthis invention are as follows:

A plate of metal having thereon two bridges, in which is planted a rack and pinion for the purpose of multiplying` the direct action of a strip composed of two metals fused together, unequal] y affected by temperature, and changing the same into a rotary motion. Secured to the plate at one end is the compound metal strip G, the other end of which is connected 2 5 with the rack I) by means of a connectinglink, thus communicating action to the rack, thence to the index-hand bymeans ot" apinion, C. rIhus far my description relates only to instruments already existing.

In manyinstruments of this class which hav heretofore been made a hair-spring has been placed on the center arbor or attached tosome part of the rack as a means of attaining steady action of the index-hand 5 but inasmuch as the turning ofthe hand and its pinion in either direction produces a constantly-increasing resistance, while the movingpower remains the same, it is apparent that in extremes of temperature the index-hand would be more or less retarded from this resistance, and thus indi- 4o cate the temperature incorrectly. This results from the lack of strength in the lateral draw of thelamina and is easily proved by the dropping which takes place in certain positions by the simple action of gravitation.

To obviate this error or defect in the correctness of mechanical thermometers is the object of my invention, and is produced :as follows, reference being had to the drawing forming part of this specification, which is a view of 5o the mechanism detached.|

To the opposite end of the metal plate I attach another bimetallic strip, G', precisely like the first mentioned and attached by the Vsame method to a point opposite and equidistant 55 from the acting center ofthe rack. In setting the two bimetallic strips, when putting the in# strumenttogether, they are so placed that there shall be a slight side` draw on the pivot of the segment, which draw or tension is maintained 6o evenly throughout its action in all extremes ot' temperature, thus securing an accurately graduated scale and perfectly steady hand, which, when properly made, shows no aberration in any position at a xed temperature.

Having thus fully described my invention, what I claim, and desire to secure by Letters Patent, is-

The combination,in a mechanical thermometer, of two bimetallic strips attached to a le- 7o ver-arm so as to Vact together in operating the indicating-hand, but so adjusted as. to have a slight tension in respect to each other, substantially as shown and described. t

WILLIAM' ATHERTON VALES.

Witnesses RUEUs FoLsoM, GEORGE H. BoURNE. 

